feat(frontend): decide on a project in its review, and filter the queue

[sabinem]

As an owner, I open a project, read it, and decide — Approve or Reject — right there. Before, I approved from a button on a list row without ever opening the project.

The queue now has three tabs, so I can look at just what's awaiting review, or just what I turned down, instead of scrolling one mixed list.

• Two buttons per project, always: the two states it isn't in. Awaiting review → Approve · Reject. Approved → Revoke approval · Reject. Rejected → Approve · Reconsider.
• Tabs are real addresses, so a filtered view can be bookmarked and the back button works.
• Opens on Approved. The Awaiting review count shows as an amber badge — it asks for attention without moving where you land.
• Deciding returns you to the tab you came from, so approving the last proposal lands on "Nothing is awaiting review" rather than quietly moving you.

Left out: clearing a queue in one click each. That's the cost of deciding in a review, and it's the point. Participants are untouched — their list was already approved-only.